Control of luteolysis in the one-humped camel (Camelus dromedarius)

Blood plasma concentrations of 13,14-dihydro-15-keto PGF(2 alpha) (PGFM) we re measured in groups of mature non-pregnant and pregnant camels to study P GF(2 alpha) release patterns around the time of luteolysis and the timing o f the signal for pregnancy recognition. Injection of each of four camels wi th 10 and 50 mg of PGF(2 alpha) showed clearly that five times the dose of exogenous hormone produced five times the amount of PGFM: in peripheral pla sma, thereby indicating that, as in other animal species, PGFM is the princ ipal metabolite of PGF(2 alpha) in the camel. Serial sampling of three non- pregnant camels on each of days 8, 10 and 12, and three pregnant camels on day 10, after ovulation for 8 h showed a significant (P < 0.05) rise in mea n plasma PGFM concentrations only on day 10 in the non-pregnant, but not th e pregnant, animals. A single intravenous injection of 20, 50 or 100 iu oxy tocin given to three groups of three non-pregnant camels on day 10 after ov ulation did not increase their basal serum PGFM concentrations. However, da ily treatment of six non-pregnant camels between days 6 and 15 (n = 3) or 2 0 (n = 3) after ovulation with 1-2 g Of the prostaglandin synthetase inhibi tor, meclofenamic acid, inhibited PGF(2 alpha) release and thereby resulted in continued progesterone secretion throughout the period of meclofenamic acid administration. These results showed that, as in other large domestic animal species, release of PGF(2 alpha) from, presumably, the endometrium c ontrols luteolysis in the dromedary camel. Furthermore, reduction in the am ount of PGF(2 alpha) released is associated with luteal maintenance and the embryonic signal for maternal recognition of pregnancy must be transmitted before day 10 after ovulation if luteostasis is to be achieved. However, t he results also indicate that, in contrast to ruminants, the release of end ometrial PGF(2 alpha) in the non-pregnant camel may not be controlled by th e release of oxytocin.